#include <fstream>
using namespace std;
int n,s[1000001];
unsigned long long sum;

ifstream f("fractii.in");
ofstream g("fractii.out");

int main()
{	f>>n;
	for(int i=2; i <= n; ++i) s[i]=i-1;
	for(int i=2; i<=n; ++i)
	{   
		sum +=s[i];
		for(int j=i+i; j<=n; j += i) s[j]-=s[i];
	}
	g<<sum * 2 + 1<<'\n';
	f.close();
	g.close();
	return 0;
}